1. Field of the Invention
The present invention relates generally to a method and a system for electrical stimulation of muscles to augment and improve muscle function. More particularly, the present invention relates to a method and a system for electrically stimulating muscles in the leg or legs of a person with impaired walking ability in order to effect improvement in the person's walking ability.
2. Description of Related Art
There are over four million adults with impairments due to stroke in the United States. An estimated 500,000 Americans have cerebral palsy and 6,000 babies are born each year in the United States with cerebral palsy. The inefficiency of walking significantly impairs the ability of individuals with stroke and cerebral palsy to maneuver in their homes, at work, and in recreation. Many other individuals have impaired walking skills due to spina bifida, muscular dystrophy, Parkinson's disease, multiple sclerosis, spinal cord injury, Downs' Syndrome, idiopathetic toe walking, and peripheral neuropathies. Electrical simulation applied to key leg muscles has shown promise for improving the walking abilities for individuals with these disorders.
The use of Functional Electrical Stimulation (FES), first called “Electrical Muscle Therapy,” was disclosed in U.S. Pat. No. 3,083,712 issued in 1963 to James E. Keegan Jr. The Keegan, Jr. invention employed electrical muscle stimulation to lift the foot during the swing phase of walking by applying small electrical currents to the dorsiflexor muscles. In adults with stroke, a disability called “drop foot” is caused by the inability to lift the toes (dorsiflex) when stepping forward in the swing phase of walking. This problem could cause the people to trip, fall, or injure themselves. The Keegan, Jr. patent, while addressing the problem of diminished muscle function that results in foot drop, offers no disclosure of how the patented invention could be applied to other muscles that participate in walking.
Over the past four decades, drop foot stimulators have been shown to be beneficial. However, this method is limited because it applies FES only to the dorsiflexors. Because these devices treat just this one problem, they do not teach the patient new motor patterns. The effects only occur when the stimulation is applied, and the patient is not re-trained to learn other muscle recruitment patterns. Moreover, drop foot is just one component of the walking deficits of adults with stroke. For example, adults with stroke do not effectively push on each step with their plantar flexors. About eighty percent of the acceleration force necessary to maintain walking comes from the plantarflexors. Nevertheless, electrical stimulation to these muscles has received little attention.